The present invention relates to an information storage apparatus including a disk array including a disk drive and a cache (volatile memory), a host, an uninterruptible power supply (UPS) for the disk array, and a UPS for the host and a control method of the same.
In a system configuration of an information storage apparatus including a disk array including a disk drive and a cache, a host, a UPS for the disk array, and a UPS for the host, when a power failure occurs, there is required, there is required a procedure to guarantee user data as follows.
Occurrence of Power Failure
{circle around (1+L )} Processing of host termination and cache flush of the disk array (to write data of the cache in the disk drive) and setting of the system to a write-through mode (to inhibit use of the cache). 
{circle around (2)} Recognition of completion of host termination
{circle around (3)} Processing of host UPS termination
{circle around (4)} Processing of disk array termination
{circle around (5)} Recognition of completion of disk array termination
{circle around (6)} Processing of termination of disk array UPS.
JP-A-8-297530 describes a technology related to the operations above.
In accordance with the technology of the publication above, only processing on the host side of {circle around (1)} and operations of {circle around (2)} and {circle around (3)} can be automatically accomplished. However, the processing on the disk array side of {circle around (1)} and operations of {circle around (4)} to {circle around (6)} are disadvantageously required to be carried out by human power. That is, when a power failure occurs on the host side, only the termination processing is required to be immediately executed; whereas, on the disk array side, the termination processing is carried out only after data of the host side are entirely received. Therefore, the termination must be achieved after the completion of the host termination is recognized and this restriction results in a difficulty.
It is therefore an object of the present invention to provide an interlock control method for each of the operations of {circle around (4)} to {circle around (6)} between the host, the disk array, and the uninterruptible power supplies to thereby automatically conduct the overall operations including the operation on the disk array side of {circle around (1)} without any intervention of human power so as to guarantee user data.
Furthermore, another object of the present invention is to provide an interlock control method for wider usability in which the operation between the disk array and the UPS and that between the host and the UPS are related to each other in the same control method. Consequently, it is possible to control the disk array and the host by the UPSs of the same configuration.
To achieve the objects above in accordance with the present invention, there is provided a method as follows.
The uninterruptible power supplies monitor a state change of the host-side power from on to off to sequentially execute processing in an order of the processing of host termination, cache flush processing of the disk array, the processing of host UPS termination, the processing of disk array termination, and the processing of disk array UPS termination.
Additionally, between the host UPS and the host and between the disk array UPS and the disk array, there is provided an interlock control signal to monitor the respective current states so as to mutually control respective operations. Consequently, the host UPS and the disk array UPS advantageously have the same configuration for wider usability.
Moreover, a single UPS to supply power to the disk array and to the host monitors the state change of the power on the host side from on to off by a small computer systems interface (SCSI) interface (I/F) or unit establishing a connection between the host and the disk array to sequentially accomplish processing in an order of the processing of host termination, the processing of cache flush of the disk array, the processing of disk array termination, and the processing of UPS termination.